history abot life

1. A wheel is a circular component that is
intended to rotate on an axle bearing. The
wheel is one of the key components of
the wheel and axle which is one of the six
simple machines. Wheels, in conjunction with
axles, allow heavy objects to be moved easily
facilitating movement or transportation while
supporting a load, or performing labor in
machines. Wheels are also used for other
purposes, such as a ship's wheel, steering
wheel, potter's wheel, and flywheel.
Common examples can be found
in transport applications. A wheel
reduces friction by facilitating motion
by rolling together with the use of axles. In
order for wheels to rotate, a moment needs to
be applied to the wheel about its axis, either
by way of gravity or by the application of
another external force or torque. Using the
wheel, Sumerians invented a device that spins
clay as a potter shapes it into the desired
object.

2. The English word wheel comes from
the Old English word hwēol,
from Proto-Germanic *hwehwlaz,
from Proto-Indo-
European *kwékwlos, an extended
form of the root *kwel- "to revolve,
move around". Cognates within
Indo-European
include Icelandic hjól "wheel,
tyre", Greek κύκλος kúklos,
and Sanskrit chakra, the last two
both meaning "circle" or "wheel".

3. The place and time of the invention of the wheel
remains unclear, because the oldest hints do not
guarantee the existence of real wheeled transport,
or are dated with too much
scatter.Mesopotamian civilization is credited with
the invention of the wheel by a number of old
sources.However, according to some relatively
recent sources the wheel was not invented in
Mesopotamia first, they suggest Eastern Europe or
that Sumerians probably acquired the wheel from
Indians and unlike other breakthrough inventions,
the wheel cannot be attributed to a single nor
several inventors. Evidence of early usage of
wheeled carts has been found across the Middle
East, in Europe, Eastern Europe, India and China. It
is not known whether Chinese, Indians and
Europeans invented the wheel independently or
not.

4. The Halaf culture of 6500–5100 BCE is sometimes
credited with the earliest depiction of a wheeled
vehicle, but this is doubtful as there is no evidence
of Halafians using either wheeled vehicles or even
pottery wheels.Precursors of pottery wheels,
known as "tournettes" or "slow wheels", were
known in the Middle East by the
5th millennium BCE. One of the earliest examples
was discovered at Tepe Pardis, Iran, and dated to
5200–4700 BCE. These were made of stone or clay
and secured to the ground with a peg in the center,
but required significant effort to turn. True potter's
wheels, which are freely-spinning and have
a wheel and axle mechanism, were developed
in Mesopotamia (Iraq) by 4200–4000 BCE. The
oldest surviving example, which was found
in Ur (modern day Iraq), dates to approximately
3100 BCE.Wheels of uncertain dates have also
been found in the Indus Valley civilization, a
4th millennium BCE civilization covering areas of
present-day India and Pakistan.

5. The oldest indirect evidence of wheeled
movement was found in the form of miniature
clay wheels north of the Black Sea before
4000 BCE. From the middle of the 4th
millennium BCE onward, the evidence is
condensed throughout Europe in the form of
toy cars, depictions, or ruts, with the oldest
find in Northern Germany dating back to
around 3400 BCE.In Mesopotamia, depictions
of wheeled wagons found on clay
tablet pictographs at the Eanna
district of Uruk, in the Sumerian civilization are
dated to c. 3500–3350 BCE. In the second half
of the 4th millennium BCE, evidence of
wheeled vehicles appeared near-
simultaneously in the Northern (Maykop
culture) and South Caucasus and Eastern
Europe (Cucuteni-Trypillian culture).

6. Depictions of a wheeled vehicle appeared between 3631
and 3380 BCE in the Bronocice clay pot excavated in
a Funnelbeaker culture settlement in
southern Poland.[20]In nearby Olszanica, a 2.2 m wide
door was constructed for wagon entry; this barn was
40 m long with three doors, dated to 5000 B.C.E—7000
years old, and belonged to the neolithic Linear Pottery
culture.[citation needed] Surviving evidence of a wheel-axle
combination, from Stare Gmajne near Ljubljana in
Slovenia (Ljubljana Marshes Wooden Wheel), is dated
within two standard deviations to 3340–3030 BCE, the
axle to 3360–3045 BCE. Two types of early Neolithic
European wheel and axle are known: a circumalpine type
of wagon construction (the wheel and axle rotate
together, as in Ljubljana Marshes Wheel), and that of
the Baden culture in Hungary (axle does not rotate). They
both are dated to c. 3200–3000 BCE.Some historians
believe that there was a diffusion of the wheeled vehicle
from the Near East to Europe around the mid-4th
millennium BCE.

7. Early wheels were simple wooden disks with a hole for
the axle. Some of the earliest wheels were made from
horizontal slices of tree trunks. Because of the uneven
structure of wood, a wheel made from a horizontal slice
of a tree trunk will tend to be inferior to one made from
rounded pieces of longitudinal boards.
The spoked wheel was invented more recently and
allowed the construction of lighter and swifter vehicles.
The earliest known examples of wooden spoked wheels
are in the context of the Sintashta culture, dating to
c. 2000 BCE (Krivoye Lake). Soon after this, horse cultures
of the Caucasus region used horse-drawn spoked-wheel
war chariots for the greater part of three centuries. They
moved deep into the Greek peninsula where they joined
with the existing Mediterranean peoples to give rise,
eventually, to classical Greece after the breaking
of Minoan dominance and consolidations led by pre-
classical Sparta and Athens. Celtic chariots introduced
an iron rim around the wheel in the 1st millennium BCE.

8. In China, wheel tracks dating to around 2200 BCE have
been found at Pingliangtai, a site of the Longshan
Culture.[24] Similar tracks were also found at Yanshi, a city
of the Erlitou culture, dating to around 1700 BCE. The
earliest evidence of spoked wheels in China comes
from Qinghai, in the form of two wheel hubs from a site
dated between 2000 and 1500 BCE.
In Britain, a large wooden wheel, measuring about 1 m
(3.3 ft) in diameter, was uncovered at the Must Farm site
in East Anglia in 2016. The specimen, dating from 1,100
to 800 BCE, represents the most complete and earliest of
its type found in Britain. The wheel's hub is also present.
A horse's spine found nearby suggests the wheel may
have been part of a horse-drawn cart. The wheel was
found in a settlement built on stilts over wetland,
indicating that the settlement had some sort of link to dry
land.

9. Although large-scale use of wheels did not occur in the Americas prior
to European contact, numerous small wheeled artifacts, identified as
children's toys, have been found in Mexican archeological sites, some
dating to approximately 1500 BCE. Some argue that the primary
obstacle to large-scale development of the wheel in the Americas was
the absence of domesticated large animals that could be used to pull
wheeled carriages.The closest relative of cattle present in Americas in
pre-Columbian times, the American bison, is difficult to domesticate
and was never domesticated by Native Americans; several horse species
existed until about 12,000 years ago, but ultimately became extinct. The
only large animal that was domesticated in the Western hemisphere,
the llama, a pack animal, was not physically suited to use as a draft
animal to pull wheeled vehicles, and use of the llama did not spread far
beyond the Andes by the time of the arrival of Europeans.
On the other hand, Mesoamericans never developed the wheelbarrow,
the potter's wheel, nor any other practical object with a wheel or
wheels.Although present in a number of toys, very similar to those
found throughout the world and still made for children today ("pull
toys"), the wheel was never put into practical use in Mesoamerica
before the 16th century.[31][32] Possibly the closest the Mayas came to
the utilitarian wheel is the spindle whorl, and some scholars believe
that these toys were originally made with spindle whorls and spindle
sticks as "wheels" and "axes".

10. A wheeled vehicle requires much less work to move than
simply dragging the same weight. The low resistance to
motion is explained by the fact that the frictional
work done is no longer at the surface that the vehicle is
traversing, but in the bearings. In the simplest and oldest
case the bearing is just a round hole through which the
axle passes (a "plain bearing"). Even with a plain bearing,
the frictional work is greatly reduced because:
The normal force at the sliding interface is same as with
simple dragging.
The sliding distance is reduced for a given distance of
travel.
The coefficient of friction at the interface is usually lower.

11. The wheel has also become a strong cultural and spiritual
metaphor for a cycle or regular repetition
(see chakra, reincarnation, Yin and Yang among others). As
such and because of the difficult terrain, wheeled vehicles
were forbidden in old Tibet. The wheel in ancient China is
seen as a symbol of health and strength and used by some
villages as a tool to predict future health and success.
The diameter of the wheel is indicator of one's future health.
The Kalachakra or wheel of time is also a subject in some
forms of Buddhism, along with the dharmachakra.[45][46]
The winged wheel is a symbol of progress, seen in many
contexts including the coat of arms of Panama, the logo of
the Ohio State Highway Patrol and the State Railway of
Thailand. The wheel is also the prominent figure on the flag
of India. The wheel in this case represents law (dharma). It
also appears in the flag of the Romani people, hinting to their
nomadic history and their Indian origins.

12. The introduction of spoked (chariot) wheels in the
Middle Bronze Age appears to have carried
somewhat of a prestige. The sun cross appears to
have a significance in Bronze Age religion,
replacing the earlier concept of a solar barge with
the more 'modern' and technologically
advanced solar chariot. The wheel was also a solar
symbol for the Ancient Egyptians.
In modern usage, the 'invention of the wheel' can
be considered as a symbol of one of the first
technologies of early civilization, alongside farming
and metalwork, and thus be used as a benchmark
to grade the level of societal progress.[citation needed]
Some Neopagans such as Wiccans have adopted
the Wheel of the Year into their religious practices.[